Silicon Oxide Negative Electrode with Carbon Coating
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Solution Overview
Problem
Lithium-ion secondary batteries using silicon materials face challenges in achieving high battery capacity and cycle performance due to the expansion and contraction of silicon active material particles, leading to electrolyte decomposition and reduced cycle stability compared to carbon-based batteries.
Innovation Solution
A negative electrode active material comprising silicon oxide (SiOx) with 0.5≦x≦1.6, partially coated with a carbon layer exhibiting specific X-ray diffraction and Raman spectrum characteristics, enhancing conductivity and electrolyte impregnation, and a method for producing this material to improve battery capacity and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as a negative electrode active material to increase battery capacity, then the battery capacity is improved, but the cycle performance deteriorates due to particle breakage and electrolyte decomposition
Solution Approach 1:
The invention uses a composite structure consisting of a silicon core and a carbon coating shell. The silicon core (SiOx with 0.5≦x≦1.6) provides high capacity, while the carbon coating layer protects the silicon from breakage and prevents electrolyte decomposition, thereby maintaining both high capacity and good cycle performance
Solution Approach 2:
The carbon coating forms a flexible protective shell around the silicon core that can accommodate volume changes during charging and discharging cycles. This shell prevents the silicon from breaking while allowing lithium ion insertion and extraction, thus improving cycle stability
2Reliability
If a carbon coating is applied to silicon particles to improve cycle performance, then the conductivity and electrolyte impregnation are enhanced, but the manufacturing complexity increases
Solution Approach 1:
The invention optimizes specific parameters of the carbon coating, including its thickness (controlled to provide adequate protection without excessive complexity), density (1.2 g/cm³ to 1.9 g/cm³), and structural properties (XRD half width of 1.5° to 4.5° at 2θ=25.5°, Raman intensity ratio I1330/I1580 of 0.7 to 2.0). These parameter specifications enable standardized manufacturing processes while achieving the desired performance improvements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The silicon-based active material with a carbon coating achieves high battery capacity, excellent cycle performance, and improved first charge and discharge efficiency, addressing the limitations of silicon materials by optimizing the carbon coating's properties and structure.
Implementation Method 1
exhibiting a peak at 2θ=25.5° having a half width of 1.5° to 4.5° in an X-ray diffraction spectrum measured after separating the carbon coating from the negative electrode active material particles
Implementation Method 2
exhibiting scattering peaks at 1330 cm−1 and 1580 cm−1 in Raman spectrum obtained by Raman spectrometry measured after separating the carbon coating from the negative electrode active material particles
Data Source
AI summary
The present invention provides a negative electrode active material for a non-aqueous electrolyte secondary battery, including negative electrode active material particles containing a silicon compound expressed by SiOx where 0.5≦x≦1.6, the negative electrode active material particles at least partially coated with a carbon coating, the carbon coating exhibiting a peak at 2θ=25.5° having a half width of 1.5° to 4.5° in an X-ray diffraction spectrum measured after separating the carbon coating from the negative electrode active material particles, the carbon coating exhibiting scattering peaks at 1330 cm−1 and 1580 cm−1 in Raman spectrum obtained by Raman spectrometry measured after separating the carbon coating from the negative electrode active material particles, wherein a ratio of an intensity of the scattering peak at 1330 cm−1 to that at 1580 cm−1 satisfies 0.7<I1330/I1580<2.0. This negative electrode active material can increase the battery capacity and improve the cycle performance and battery initial efficiency.